A belt drive normally comprises an infinite belt and at least two pulleys, of which one can serve as a drive and one as an output of the belt drive. Such belt drives are especially used in internal combustion engines of a motor vehicle for driving auxiliary units, wherein a first pulley is arranged on the crankshaft of the internal combustion engine and drives the belt. Further belt pulleys are associated with the auxiliary units, as for example a water pump, a generator or an air conditioning compressor, and are rotatingly driven by the belt drive. In common belt drives the auxiliary units, which can also be referred to as accessories or ancillary assemblies, are designed as consumers, i.e. they are driven by the belt pulley of the crankshaft via the belt. In this case, the undriven side of the belt is arranged between the crankshaft and the unit, generally the generator, following in the circumferential direction of the belt. To ensure a sufficient belt wrap around the belt pulley, the belt is pretensioned by a tensioning roller of the belt tensioning device.
From EP 2 573 423 A1 a belt tensioning device is known for a belt drive of said type. The belt tensioning device comprises a base member on which a tensioning arm is pivotably supported. The belt tensioning device is designed such that in a mounted condition, the pivot axis of the tensioning arm is arranged inside the outer diameter of the belt pulley of the assembly.
Efforts to reduce fuel consumption and CO2 emissions accompany the need to reduce the weight of vehicle components. Thus, in the field of belt tensioning devices attempts also are being made to reduce weight.
From the applicant's DE 10 2014 206 716 A1, a belt tensioning device for a belt drive is known that comprises a base member, a tensioning arm which is pivotable relative thereto, and a spring which resiliently supports the tensioning arm in the circumferential direction. The base member and the tensioning arm at least partly consist of plastics, so that the belt tensioning device, overall, comprises a low weight.
In particular in compactly designed belt tensioning devices, high rotational variations in the belt drive, which are caused when changing from engine operation to starter operation, can lead to a high friction power and corresponding thermal loads on the belt tensioning device.